Copper having excellent electrical and thermal conductivity has been widely used in various kinds of industrial field as connectors, relays, electrodes, contact points, trolley lines, connection terminals, welding tips, rotor bars used in motors, wire harnesses, and wiring materials of robots or airplanes. For example, copper has been used for wire harnesses of cars, and weights of the cars need to be reduced to improve fuel efficiency regarding global warming. However, the weights of used wire harnesses tend to increase according to high information, electronics, and hybrids of the car. Since copper is expensive metal, the car manufacturing industry wants to reduce the amount of copper to be used in view of the cost. For this reason, if a copper wire for a wire harness which has high strength, high conductivity, flexibility, and excellent ductility is used, it becomes possible to reduce the amount of copper to be used thereby allow achieving a reduction in weight and cost.
There are several kinds of wire harnesses, for example, a power system and a signal system in which only very little current flows. For the former, conductivity close to that of pure copper is required as the first condition. For the later, particularly, high strength is required. Accordingly, a copper wire balanced in strength and conductivity is necessary according to purposes. Distribution lines and the like for robots and airplanes are required to have high strength, high conductivity, and flexibility. In such distribution lines, there are many cases of using a copper wire as a stranded wire including several or several tens of thin wires in structure to further improve flexibility. In this specification, a wire means a product having a diameter or an opposite side distance less than 6 mm. Even when the wire is cut in a rod shape, the cut wire is called a wire. A rod means a product having a diameter or an opposite side distance of 6 mm or more. Even when the rod is formed in a coil shape, the coil-shaped rod is called a rod. Generally, a material having a large outer diameter is cut in a rod shape, and a thin material comes out into a coil-shaped product. However, when a diameter or an opposite side distance is 4 to 16 mm, there are wires and rods together. Accordingly, they are defined herein. A general term of a rod and a wire is a rod wire.
A high strength and high conductivity copper alloy pipe, rod, or wire (hereinafter, referred to as a high performance copper pipe, rod, or wire) according to the invention requires the following characteristics according to usage.
Thinning on the male side connector and a bus bar is progressing according to reduction in size of the connector, and thus strength and conductivity capable of standing against putting-in and drawing-out of the connector is required. Since a temperature rises during usage, a stress relaxation resistance is necessary.
In a relay, an electrode, a connector, a buss bar, a motor, and the like, in which large current flows, high conductivity is naturally required and also high strength is necessary for compact size or the like.
In a wire for wire cut (electric discharging), high conductivity, high strength, wear resistance, high-temperature strength, and durability are required.
In a trolley line, high conductivity and high strength are required, and durability, wear resistance, and high-temperature strength are also required during usage. Generally, since there are many trolley lines having a diameter of 20 mm, the trolley lines fall within the scope of rod in this specification.
In a welding tip, high conductivity, high strength, wear resistance, high-temperature strength, durability, and high thermal conductivity are required.
In the viewpoint of high reliability, soldering is not used, but brazing is generally used for connection among electrical members, among high-speed rotating members, among members with vibration such as a car, and among copper materials and nonferrous metal such as ceramics. As a brazing material, for example, there is 56Ag-22Cu-17Zn-5Sn alloy brazing such as Bag-7 described in JIS Z 3261. As a temperature of the brazing, a high temperature of 650 to 750° C. is recommended. For this reason, in a rotor bar used in a motor, an end ring, a relay, an electrode, or the like, heat resistance for 700° C. as a brazing temperature is required even for a short time. Naturally, it is used electrically, and thus high conductivity is required even after the brazing. Centrifugal force of the rotor bar used in a motor is increased by high speed, and thus strength for standing against the centrifugal force is necessary. In an electrode, a contact point, a relay which is used in a hybrid car, an electric car, and a solar battery and in which high current flows, high conductivity and high strength are necessary even after the brazing.
Electrical components, for example, a fixer, a brazing tip, a terminal, an electrode, a relay, a power relay, a connector, a connection terminal, and the like are manufactured from rods by cutting, pressing, or forging, and high conductivity and high strength are required. In the brazing tip, the electrode, and the power relay, additionally, wear resistance, high-temperature strength, and high thermal conductivity are required. In these electrical components, brazing is often used as bonding means. Accordingly, heat resistance for keeping high strength and high conductivity even after high-temperature heating at, for example, 700° C. is necessary. In this specification, heat resistance means that it is hard to be recrystallized even by heating at a high temperature of 500° C. or higher and strength after the heating is excellent. In mechanical components such as nuts or metal fittings of faucets, a pressing process and a cold forging process are performed. An after-process includes rolling and cutting. Particularly, formability in cold, forming easiness, high strength, and wear resistance are necessary, and it is required that there is no stress corrosion cracking. In addition, there are many cases of employing the brazing for connecting pipes or the like, and thus high strength after the brazing is required.
In copper materials, pure copper based on C1100, C1020, and C1220 having excellent conductivity has low strength, and thus a using amount thereof is increased to widen a sectional area of a used part. In addition, as high strength and high conductivity copper alloy, there is Cr—Zr copper (1% Cr-0.1% Zr—Cu) that is solution-aging precipitation alloy. However, this alloy is made into a rod, generally through a heat treatment process of hot extruding, heating of materials at 950° C. (930 to 990° C.) again, rapid cooling just thereafter, and aging, and then it is additionally processed in various shapes. A product is made through a heat treatment process of a plasticity process such as hot or cold forging of an extruded rod after hot extruding, heating at 950° C. after the plasticity process, rapid cooling, and aging. As described above, the high temperature process such as at 950° C. requires large energy. In addition, since oxidation loss occurs by heating in the air and diffusion easily occurs due to the high temperature, sticking among materials occurs and thus a pickling process is necessary. For this reason, a heat treatment at 950° C. in inert gas or vacuum is performed, but a cost for the heat treatment is increased and extra energy is necessary. In addition although it is possible to prevent the oxidation loss, the problem of the sticking is not solved. In Cr—Zr copper, a scope of a solution temperature condition is narrow, and sensitivity of a cooling rate is high. Accordingly, a particular management is necessary. Moreover, Cr—Zr copper includes a large amount of active Zr and Cr, and thus there is a limitation in casting and forging. As a result, characteristics are excellent, but costs are increased.
A copper material that is an alloy composition containing 0.15 to 0.8 mass % of Sn and In in total and the remainder including Cu and inevitable impurities, has been known (e.g., Japanese Patent Application Laid-Open No. 2004-137551). However, strength is insufficient in such a copper material.